A 0.145-kg baseball pitched horizontally at 39 m/s strikes a bat and is popped straight up to a height of 31 m. If the contact time between the bat and the ball is 2.35 ms, calculate the average force [exerted by the bat on the ball] during contact. [Let the positive axis lie along the line from the batter to the pitcher, with the batter at the origin.] I'm really having trouble with this problem